In this technical field, a variety of techniques for improving the quality of radio transmitted uplink signals are used. One of the techniques relates to a transmission power control method. In this technique, the reception quality of an uplink pilot channel transmitted from a mobile station and received at a base station is measured. Then, path loss and/or other factors may be evaluated, and the transmission power for the mobile station is determined to compensate for the factors. The determined transmission power is reported to the mobile station. In this manner, a certain quality level of the received signals can be assured at the base station. Another technique for improving the signal quality relates to Adaptive Modulation and channel Coding (AMC) method. The AMC method may achieve the best possible throughput under the current communication conditions by adaptively changing modulation level and coding rate depending on the quality of radio channels. The AMC method is used in High Speed Downlink Packet Access (HSDPA) scheme, for example. The HSDPA is described in detail in non-patent document 1, for example.
In this manner, the throughput can be improved by setting transmission parameters such as the transmission power and the modulation level appropriately. The throughput may include respective user throughputs as well as the overall system throughput, and it is desirable to improve both the user throughputs and the system throughput. In particular, there may be demand of further improved throughput in future communication systems. For this reason, it is much more important to adapt the transmission parameters for the channel quality, which is referred to as “link adaptation”, for improved signal transmission quality.
Non-patent document 1: 3GPP TR25.848: “Physical Layer Aspects of UTRAN High Speed Downlink Packet Access”